The present invention relates to a color image forming apparatus in which a toner image can be formed on a belt-like image forming body in an electrophotographic way and transferred to a transfer material to reproduce an image.
There have been many prior disclosures about reproduction of a color image. The apparatus of a type, for example, in Japanese Patent O.P.I. (Open to Public Inspection) No. 100770/1986 can obtain a color copy in a way such that a latent image is formed and developed on a photosensitive drum which is an image forming body according to a number of color separations of an original. The latent image is transferred onto a transfer drum to form a multi-color image upon every development, and is then transferred to a sheet of recording paper. In addition to the photosensitive drum, the apparatus of the type described needs an additional transfer drum of a size on which one sheet of image can be transferred. It is therefore necessary to make the apparatus large in size and complicated.
The apparatus of another type, for example, in Japanese Patent O.P.I (Open to Public Inspection) No. 14992/1986 can obtain a multi-color copy in a way such that a latent image is formed and developed on a photosensitive drum according to a number of color separations of an original, the latent image being transferred onto a transfer material upon every development. In the apparatus of the type described, however, it is difficult to precisely overlap a number of color image components to obtain a quality color copy.
The apparatuses of the other type proposed by the applicant in Japanese Patent Application O.P.I. Nos. 75850/1985, 76766/1985, 95456/1985, 95458/1985 and 158475/1985 can obtain a color image in a basic multi-color image forming process such that latent image formation and color toner development are repeated a number of times equal to the number of color image separations on a photosensitive drum, the color toner images being overlapped on the photosensitive drum, and transference then being made. In the multi-color image forming apparatuses of the type described in which the overlapping method is used, a plurality made. In the multi-color image forming apparatuses of the type described in which the overlapping method is used, a plurality of developing means for different colors ar provided around the photosensitive drum which usually has to be revolved a multiple number of times to develop the latent image thereon to produce the color image.
It has been proposed that the image forming body be the photosensitive drum mentioned above, with a photoconductive material is coated or evaporated on an outside portion thereof. There also was proposed a belt-like image forming body on which the photoconductive material is coated or attached on a flexible belt. The belt-like image forming body (hereinafter referred to as the photosensitive belt) is effective to make use of possible space limitations because its shape can be determined by the photosensitive belt provided between revolving rollers including a drive roller. This allows the color image forming apparatus to be made compact.
The photosensitive belt can be run along a small curvature with use of the revolving roller of a small diameter. The small curvature portion can be used to separate a transferring material. This prevents insufficient separation of the transferring material.
The photosensitive drum of another type proposed, for example, in Japanese Patent Application O.P.I. No. 48350/1988 is made in the way such that the photosensitive drum can collect used toner therein. Also, the used toner collecting container of a type proposed, for example, in Japanese Patent Application O.P.I. No. 150782/1981 can be dispensed of in view of a life balance of the amount of used toner in a photosensitive drum and photosensitive paper wrapped on it. These proposals aim at making the apparatus small in size and compact.
However, in both of the above-described used toner collecting apparatuses, the types and materials of the photosensitive drums are related to service life of the apparatuses. Particularly, a toner carrying mechanism for carrying the toner to a revolving drum body is complicated, being defective in leakage and splashing of the toner. The used toner collecting apparatuses cannot always be made compact at low costs.
The color image forming apparatus using the photosensitive belt described above has image forming means, including an electricity charging means, an image exposing means, a plurality of developing means, and cleaning means, provided to be faced primarily with a lower outside portion of the photosensitive belt. These image forming means are integrated together with the photosensitive belt into a single module in the form of a process cartridge so that it can be independently attached to or detached from the main body.
Accordingly, a toner supply container containing a toner supply for the developing means and a closed used toner container for containing the used toner collected by the cleaning device have to be provided at positions where they can be functionally coupled with the process cartridge. It is however difficult to integrate them with the developing means and cleaning device in view of different service lives and maintenance service work.
In view of the foregoing, it is a first object of the present invention to provide a color image forming apparatus in which a toner supply container and a closed used toner container can be easily attached to or detached from a process cartridge as necessary.
Further in view of the foregoing, if many image forming means are integrated into a single module, the cartridge is made large and heavy. It is not only difficult to attach to or detach from the main body, but also inconvenient in connection with maintenance service as every image forming means is different in service life and maintenance frequency. Accordingly, it is a second object of the present invention to propose a color image forming apparatus in which the image forming means such as the photosensitive belt can be attached to or detached from the main body in a very easy way so that they will not interfere each other with respect to maintenance and checking.
Other objects of the invention will become obvious from the contents of the specification herein after disclosed